基于嵌入压电技术的钢管核心混凝土缺陷检测

钢管混凝土构件核心混凝土缺陷影响到其延性和承载力。利用自制的嵌入式压电功能元,该文提出了基于压电陶瓷应力波测量与分析的核心混凝土缺陷监测方法。通过对比不同状态简谐激励下测量信号幅值和扫频激励下小波包能量的差异,定义了基于测量信号幅值和小波包能量的损伤指标。结果表明,利用所提出的嵌入式压电技术和所定义的损伤指标,有效地识别了钢管混凝土构件的核心混凝土损伤,损伤指标对损伤程度敏感。     

激光陀螺用压电陶瓷材料的制备与研究

通过文献调研设计了压电陶瓷配方,使用传统固相法制备目标压电陶瓷以达到大应变要求,以应用于激光陀螺激光稳频器中,通过r(Zr)/r(Ti)系列实验可得r(Zr)/r(Ti)=46/54组成在1 180℃烧结时获得最佳的压电介电性能,即压电常数d33≈640pC/N,弹性刚度系数cE11=60.61GPa,相对介电常数εT33/ε0≈3 300,介电损耗tanδ≈1.85%,机电耦合系数kp=0.655,居里温度TC=272℃。X线衍射(XRD)分析确认相界组成为r(Zr)/r(Ti)=46/54,扫描电镜(SEM)表明烧结温度对陶瓷晶粒尺寸有显著影响,在1 180~1 200℃之间晶粒尺寸显著增大。     

Integrating embedded piezoelectric sensors with continuous wavelet transforms for real-time concrete curing strength monitoring

It is highly necessary to evaluate strength development during the curing process to ensure the quality of concrete in construction using concrete. In particular, curing strength monitoring at early age is very important to reduce the construction cost and time, because it can provide the information required for the decision-making to safely progress to the next process. In this study, a guided wave-based non-destructive curing strength gain monitoring method that can be used even for early-age concrete is proposed. A steel plate-type piezoelectric sensor module was embedded in the concrete media at the same time as concrete placement to measure the signal from early-age concrete. The guided wave signals were measured continuously using the pitch-catch method at regular intervals. The wavelet transform process was performed to improve the quality of the signal. The guided wave's velocity of each measurement time was varied by extracting the time of flight. The wave velocity hysteresis curve according to the curing age was traced to analyse the variation patterns. Finally, a specific equation to estimate the curing strength without destructive test was derived using regression analysis based on the wave velocity hysteresis and the results from the compression test.     

Electroactive phases of poly(vinylidene fluoride): Determination,processing and applications

Poly(vinylidene fluoride), PVDF, and its copolymers are the family of polymers with the highest dielectric constant and electroactive response, including piezoelectric, pyroelectric and ferroelectric effects. The electroactive properties are increasingly important in a wide range of applications such as in biomedicine, energy generation and storage, monitoring and control, and include the development of sensors and actuators, separator and filtration membranes and smart scaffolds, among others. For many of these applications the polymer should be in one of its electroactive phases. This review presents the developments and summarizes the main characteristics of the electroactive phases of PVDF and copolymers, indicates the different processing strategies as well as the way in which the phase content is identified and quantified. Additionally, recent advances in the development of electroactive composites allowing novel effects, such as magnetoelectric responses, and opening new applications areas are presented. Finally, some of the more interesting potential applications and processing challenges are discussed.     

分散剂在sol-gel法制备PZT粉体中的应用

采用sol-gel法制备了PZT纳米粉体。针对硝酸铅会从干凝胶中析出的问题,分析了硝酸铅的析出原因,采取在溶胶中加入柠檬酸三铵作为分散剂来消除硝酸铅的偏析。实验结果表明:当柠檬酸三铵的加入量为醋酸铅的2.5%(摩尔分数)时,能得到粒度较为均匀,组成与计算配方一致的PZT纳米粉体。     

基于LMS算法的移相干涉仪环境振动控制器

环境振动严重影响移相干涉测量的过程。在运用光学外差法测得移相干涉仪环境振动信号的前提下,设计了采用高速DSP芯片的振动控制器,它对电压形式的振动信号进行采样,用自适应LMS算法分析振动信号,同时输出反馈控制信号。反馈控制信号驱动PZT光学移相器对振动引起的光程差(或波前相位)变化进行实时补偿。通过这种闭环控制,系统能够对幅频积小于100waves*Hz的环境振动进行有效补偿,实验中获得了稳定的移相干涉条纹,保证了光学测试的正确性。     

PZT纳米晶的改进型溶胶-凝胶法制备及其生长过程研究

以乙二醇为溶剂,硝酸锆为锆源,采用改进的溶胶-凝胶法,通过优化工艺参数制备了纳米Pb(Zr0.52Ti0.48)O3(PZT).通过对工艺条件研究, 揭示了体系的凝胶化可通过升高温度和增加pH值来实现.通过对溶胶的红外光谱分析给出了溶胶、凝胶形成的机理.通过TG-DTA、XRD、SEM、TEM等手段对从凝胶到PZT纳米晶的生长过程及性能进行了表征.实验证明,改进后工艺简单易行,溶胶稳定,干凝胶在650℃热处理2h,获得较完整的钙钛矿型PZT,粒径约为50～100nm.     

压电薄膜喷流泵研究

将压电流体驱动技术和仿生技术、喷流推进技术结合,提出了一种新型的压电喷水推进装置,并对该装置的核心部件—压电喷流泵进行了研究。详细分析和介绍了泵的结构及工作原理,设计制作了实验用样机,并进行了性能测试。实验测试表明,该泵工作性能稳定,喷流量大,在正弦信号激励下,电压为190 V,工作频率为140 Hz时,最大喷流量可达到714 ml/min。     

新型集成三维微力检测微夹持器

提出了一种以压阻检测技术为基础,压电陶瓷为微驱动元件,具有两级位移放大且集成三维微力传感器的微夹持器。采用有限元软件对微操持器放大机构和传感器弹性体进行分析,并给出了传感器的标定方法。实验证明,该传感器具有无耦合、测量分辨率高、线性度好、标定简单的优点,满足了预计的设计要求,传感器最大量程为10 mN,X向与Y向的分辨率均为2.4 μN,Z向的分辨率为4.2 μN;同时也验证了所设计的微夹持器的合理性和实用性,当压电陶瓷驱动电压取200 V时,微夹持器的张合量达到最大值274 μm。     

压电陶瓷微纳米伸缩量测试系统

介绍了一种压电陶瓷的微纳米伸缩量的测试系统。该系统是通过调节加在陶瓷管内外管壁上的电压变化来实现陶瓷管的伸缩,其驱动电压由计算机编程并经过D/A转换后输出,再依次通过低压和高压放大后加在陶瓷管壁上。压电陶瓷的伸缩量则由电感测微仪进行测定。实验结果表明,利用该系统可以很方便地测量压电陶瓷管的伸缩,其伸缩量随着电压的变化而变化,但并非成简单的线性关系,而是呈一条曲线。